U.S. patent application number 10/387140 was filed with the patent office on 2004-07-22 for epoxy ebonite compositions.
This patent application is currently assigned to 3L&T, Inc.. Invention is credited to Chang, Rong Jong, Mazeika, Linas, Rojasova, Edita.
Application Number | 20040143037 10/387140 |
Document ID | / |
Family ID | 32716976 |
Filed Date | 2004-07-22 |
United States Patent
Application |
20040143037 |
Kind Code |
A1 |
Chang, Rong Jong ; et
al. |
July 22, 2004 |
Epoxy ebonite compositions
Abstract
Overall, ebonite coatings or elastomeric linings are not
recommended for direct immersion in sulfuric acid with higher than
65% concentration. By blending a chemical resistant epoxy resin to
an ebonite coating, the resulting epoxy ebonite composition can be
employed in more severe environment such as direct immersion in
>65% sulfuric acid. In particular, the present invention
provides a blend of an epoxy coating with an ebonite coating with a
mix ratio of 95/5 to 5/95, the resulting epoxy ebonite composition
of which has greatly increased adhesion to steel and excellent
resistance to undercut corrosion when subjected to salt spray. The
epoxy ebonite composition according to the present invention can be
used as coatings, adhesives, encapsulants or sealants and is
particularly useful as industrial coatings that are subject to wide
temperature variations, salt contamination or chemical attack.
Inventors: |
Chang, Rong Jong; (Fremont,
CA) ; Rojasova, Edita; (Cupertino, CA) ;
Mazeika, Linas; (San Carlos, CA) |
Correspondence
Address: |
LUMEN INTELLECTUAL PROPERTY SERVICES, INC.
2345 YALE STREET, 2ND FLOOR
PALO ALTO
CA
94306
US
|
Assignee: |
3L&T, Inc.
Mountain View
CA
94043
|
Family ID: |
32716976 |
Appl. No.: |
10/387140 |
Filed: |
March 11, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60441075 |
Jan 17, 2003 |
|
|
|
Current U.S.
Class: |
523/400 |
Current CPC
Class: |
C09D 163/00 20130101;
C09D 121/00 20130101; C08K 3/04 20130101; C09D 121/00 20130101;
C08K 5/0025 20130101; C09D 163/00 20130101; C08K 3/013 20180101;
C08L 2666/54 20130101; C08L 2666/14 20130101; C08L 63/00 20130101;
C08K 3/36 20130101 |
Class at
Publication: |
523/400 |
International
Class: |
C08L 063/00 |
Claims
We claim:
1. An epoxy-ebonite composition useful for protecting metal from
undercut corrosion or chemical attack, said epoxy-ebonite
composition comprising: a mixture of epoxy/ebonite in a ratio of
95/5 to 5/95 by mass, wherein said epoxy is characterized as a high
bake epoxy composition comprising an epoxy resin and an epoxy
curing agent, and wherein said ebonite is characterized as a liquid
ebonite composition comprising a liquid rubber, a sulfur
vulcanization agent, a vulcanization accelerator, and a
vulcanization activator.
2. The epoxy-ebonite composition according to claim 1, wherein mass
parts of said liquid rubber is about 15-85; mass parts of said
sulfur vulcanization agent is about 10-50; mass parts of said
vulcanization accelerator is about 0.2-5; and mass parts of said
vulcanization activator is about 1-35.
3. The epoxy-ebonite composition according to claim 2, wherein said
liquid rubber further comprises a compatible liquid unsaturated
rubber encompassing more than 50 percent of said liquid rubber; a
non-compatible liquid unsaturated rubber; and a liquid saturated
rubber encompassing less than 10 percent of said liquid rubber.
4. The epoxy-ebonite composition according to claim 2, further
comprising: carbon black having mass parts of about 1-10; fillers
having mass parts of about 0-5; additives having mass parts of
about 0-65; and crosslinker for said liquid rubber having mass
parts of about 0-35.
5. The epoxy-ebonite composition according to claim 4, wherein said
crosslinker enables curing of said epoxy-ebonite composition at
ambient temperature.
6. The epoxy-ebonite composition according to claim 1, wherein mass
parts of said epoxy resin is about 35-75; and mass parts of said
epoxy curing agent is about 12-65.
7. The epoxy-ebonite composition according to claim 6, wherein said
epoxy curing agent is selected from aliphatic amines, amidoamines,
cycloaliphatic amines, aromatic amines, and anhydrides.
8. The epoxy-ebonite composition according to claim 6, further
comprising: silica having mass parts of about 0-25; thixotropic
agent having mass parts of about 0-5; and pigments and fillers
having mass parts of about 0-40.
9. The epoxy-ebonite composition according to claim 8, wherein said
silica is selected from the group consisting of precipitated
silica, fume silica, fused silica, colloidal silica, and silica
sand.
10. The epoxy-ebonite composition according to claim 1, further
comprising: an organic solvent.
11. The epoxy-ebonite composition according to claim 1, wherein
said liquid rubber has a general formula:
F.sub.1--(CH.sub.2--CR.sub.1.dbd.CH--
-CH.sub.2).sub.x--(CH.sub.2--CR.sub.2R.sub.3).sub.y-M.sub.2-F.sub.2,
where R.sub.1=H, CH.sub.3, or Cl; R.sub.2, R.sub.3=H, CH.sub.3,
C.sub.2H.sub.5, phenyl, nitrile, acrylate, acetate, vinyl, Cl, or
Br; F.sub.1, F.sub.2=H, CH.sub.3, OH, COOH, NH.sub.2, NCO, epoxy,
vinyl, acrylate, methacrylate, or anhydride; M is ethylidene
norbornene, hexadiene, or dicyclopentadiene; and
5<x+y+z<150.
12. The epoxy-ebonite composition according to claim 1, wherein
said liquid rubber contains at least 50 percent by mass of an
unsaturated liquid rubber that is substantially compatible with
said epoxy resin.
13. The epoxy-ebonite composition according to claim 12, wherein
said substantially compatible unsaturated liquid rubber is selected
from the group consisting of epoxidized liquid rubber, nitrile
rubber, maleinized liquid rubber, acrylic functional liquid rubber,
and chloroprene rubber.
14. The epoxy-ebonite composition according to claim 1, wherein
said liquid rubber contains 0-10 percent by mass of a saturated
liquid rubber.
15. The epoxy-ebonite composition according to claim 14, wherein
said saturated liquid rubber is selected from the group consisting
of butyl rubber, chlorobutyl rubber, bromobutyl rubber, ethylene
propylene copolymer, and ethylene propylene diene copolymer.
16. The epoxy-ebonite composition according to claim 1, wherein
said liquid rubber further comprises reactive functional group.
17. The epoxy-ebonite composition according to claim 16, wherein
said reactive functional group is selected from the group
consisting of hydroxyl, isocyanate, epoxy, amine, maleic anydirde,
and carboxylic acid.
18. The epoxy-ebonite composition according to claim 1, wherein
said sulfur vulcanization agent is selected from the group
consisting of elemental sulfur, insoluble sulfur, and organic
sulfur donor.
19. The epoxy-ebonite composition according to claim 1, wherein
said vulcanization activator is selected from the group consisting
of zinc oxide, magnesium oxide, zinc salt of carboxylic acids, and
magnesium salt of carboxylic acids.
20. The epoxy-ebonite composition according to claim 1, wherein
said vulcanization accelerator is selected from the group
consisting of thiuram, tetramethylthiuram disulfide,
tetrabutylthiruram disulfide, tetraisobutylthiuram disulfide,
tetrabenzylthiuram disulfide, tetraalkylthiuram disulfide,
2-mercaptobenzothiazole, benzothiazyl disulfide,
N-oxydiethylenebenzothiazole-2-sulfenamide,
N-cyclohexyl-benzothiazole-2-sulfenamide,
N-tert-butyl-2-benzothiazolesul- fenamide, diphenylguanidine,
N,N'-ditolylguanidine, aldehyde-aniline condensation products,
bismuth dimethyldithiocarbamate, cadmium dimethyldithiocarbamate,
cadmium diethyldithiocarbamate, copper dimethyldithiocarbamate,
lead dimethyldithiocarbamate, selenium dimethldithiocarbamate,
selenium diethyldithiocarbamate, tellurium dimethyldithiocarbamate,
zinc dimethyldithiocarbamate, zinc diethyldithiocarbamate, zinc
di-n-butyldithiocarbamate, zinc diamyldithiocarbamate, thiodiazine,
diethylthiourea, trimethylthiourea, dibuylthiourea, and zinc
isopropyl xanthate.
21. The epoxy-ebonite composition according to claim 1, wherein
said epoxy resin is selected from the group consisting of bisphenol
A diglycidyl ether, bisphenol F diglycidyl ether, phenolic epoxy,
phenol novolac epoxy, cresol novolac epoxy,
tris(hydroxylphenyl)methane triglycidylether, triglycidyl
p-aminophenol, tetraglycidyl amine of methylenedianiline,
1,3,5-tris(2,3-epoxypropyl)-1,3,5-perhydrotriazine-2,- 4,6-trione
(triglycidyl isocyanurate), and polyglycidylether of
poly(4-hydroxylstyrene).
22. The epoxy-ebonite composition according to claim 1, wherein
said mixture is baked at greater than 90.degree. C. but less than
200.degree. C. for at least 5 minutes but less than 120
minutes.
23. The epoxy-ebonite composition according to claim 1, wherein
said mixture is pre-mixed according to a desired ratio and supplied
as a single component system for applying directly onto a metal
substrate.
24. The epoxy-ebonite composition according to claim 1, wherein
said high bake epoxy composition and said liquid ebonite
composition are supplied separately as a two-component system and
mixed according to a desired ratio into said mixture for applying
onto a metal substrate.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application relates a U.S. provisional patent
application No. 60/441,075, filed Jan. 17, 2003 and titled
"CHEMICAL RESISTANT EPOXY COMPOSITION".
FIELD OF THE INVENTION
[0002] This invention generally relates to epoxy ebonite blends
and, more particularly, to an epoxy ebonite composition resulted
from a blend of an epoxy coating with an ebonite coating, the
composition of which can be used as coatings, adhesive,
encapsulants, or sealants, and of which is particularly useful as
industrial coatings which are subject to wide temperature
variations, salt contamination, corrosion, chemical attack, or the
like.
DESCRIPTION OF THE BACKGROUND ART
[0003] Epoxy resin is one of the most widely used coatings for
protecting steel due to its excellent chemical, corrosion
resistance and versatility. Epoxy coatings can be formulated with a
wide variety of starting resins such as Bisphenol A, Bisphenol F,
Novolac Epoxy, and phenolic as well as a wide selection of curing
agents such as polyamide amines, aliphatic amines, cycloaliphatic
amines, aromatic amines and anhydrides. Also, epoxy coatings are
available in liquid as well as in powder forms. An excellent
summary of using epoxy protective coatings can be found in
"Corrosion Prevention by Protective Coatings," Chapter 5, Second
Edition, by Charles Munger, published by the National Association
of Corrosion Engineers (NACE).
[0004] The adhesion of epoxy resin to steel, while depending on the
selection of curing agents, is generally satisfactory if the
service temperature does not vary too much. However, it is well
known in the coating industry that epoxy resins are prone to
interfacial delamination which prevents it from many applications
where there is a significant temperature cycling. Moreover, epoxy
has low resistance to undercut corrosion. This means that if
corrosion is initiated somewhere in the coating due to imperfection
such as pin holes or holidays, the corrosion will quickly spread
underneath the well coated areas where excellent adhesion between
the epoxy and steel was originally achieved.
[0005] On the other hand, liquid ebonite has also been disclosed as
monolithic protective coating to replace hard-rubber (or elastomer)
sheet linings to protect steel. For prior art teachings on liquid
ebonite coatings, readers are referred to U.S. Pat. Nos. 5,766,687
and 5,997,953, both by Rappoport, WO 0,006,639 by Figovsky, DE
3,740,181 by Petrovic et al., U.S. Pat. No. 6,482,894 by Chang et
al., and U.S. patent application 2002/0002244 by Hoelter et al.
[0006] Ebonite coatings exhibit several outstanding properties
including excellent adhesion to steel, resistance to delamination
due to temperature cycling, and chemical resistance to a wide range
of chemicals similar to their elastomeric sheet lining
counterparts. A summary of the chemical resistance of elastomeric
sheet linings can be found in "Coatings and Linings for Immersion
Service, Revised Edition," Chapter 9: Elastomeric Linings,
published by NACE. Overall, ebonite coatings or elastomeric linings
are not recommended for direct immersion in sulfuric acid with
higher than 65% concentration. This restricts the applications of
ebonite coatings to less severe conditions.
[0007] A liquid ebonite composition contains at least four major
ingredients: liquid rubber, elemental sulfur, vulcanization
accelerator, and vulcanization activator. There exist prior art
compositions consisting of a blend of epoxy with liquid rubber
alone, or of a blend of epoxy with sulfur or sulfur containing
organic chemicals alone. For example, it is well known and widely
practiced in the art to toughening an epoxy with a compatible
liquid rubber. As described in U.S. Pat. No. 4,921,912, such
composition provides improved physical properties such as peel
adhesion, impact strength. However, there is no mention of
corrosion resistance.
[0008] Blending an epoxy with sulfur or sulfur containing organic
chemicals alone is also well known. For example, U.S. Pat. No.
4,389,501, disclosed that by adding elemental sulfur to an epoxy
composition, the cure rate of the epoxy was accelerated. However,
there was no mention of effect on adhesion or resistance to
undercut corrosion. U.S. Pat. No. 4,153,740, disclosed an
organo-sulfur compound such as thiuram, sulfenamide, or
benzothizole in a resinous carrier including epoxy as a coating on
the electrical wire for detecting wire overheating. All the
organo-sulfur compounds disclosed therein can be used as a
vulcanization accelerator. This prior art composition thus
contained an epoxy and a vulcanization accelerator, but not liquid
rubber, elemental sulfur, and vulcanization activator that are
required in an ebonite composition.
[0009] These prior art teachings do not teach or suggest an epoxy
composition that contains the four essential ingredients of a
liquid ebonite composition, namely, liquid rubber, elemental
sulfur, vulcanization accelerator, and vulcanization activator.
Furthermore, none of the aforementioned prior art references teach
or suggest a versatile, practical, and effective coating
composition that has improved resistance to undercut corrosion.
SUMMARY OF THE INVENTION
[0010] Overall, ebonite coatings or elastomeric linings are not
recommended for direct immersion in sulfuric acid with higher than
65% concentration. This restricts the applications of ebonite
coatings to less severe conditions. According to one important
aspect of the present invention, we have found that the addition of
liquid ebonite or hard-rubber as a minor ingredient to the epoxy
formulations greatly improves the resistance to delamination and
undercut corrosion of epoxy resins. By blending an chemical
resistant epoxy resin to the ebonite coating, the resulting ebonite
coatings can be employed in more severe environment such as direct
immersion in >65% sulfuric acid.
[0011] In particular, we have discovered rather surprisingly that a
blend of an epoxy coating with an ebonite coating with a mix ratio
of 95/5 to 5/95, resulted in a composition which greatly increased
the adhesion to steel and also exhibited excellent resistance to
undercut corrosion when subjected to salt spray. The composition
according to the present invention can be used as coatings,
adhesives, encapsulants or sealants. The present invention is
particularly useful as industrial coatings that are subject to wide
temperature variations, salt contamination or chemical attack.
DETAILED DESCRIPTION OF THE INVENTION
[0012] The above-referenced provisional patent application No.
60/441,075, filed on Jan. 17, 2003 by the present inventors,
disclosed an epoxy composition that exhibited exceptionally good
chemical resistance. Specifically, the chemical resistant epoxy
composition disclosed therein, which comprises epoxy resin of 100
parts by weight and precipitated silica of 5-65 parts, is highly
resistant to chemical attack and can be advantageously used for
short or long term direct, total, continuous, or intermittent
immersion service, such as interior and exterior protective
coatings, adhesives, encapsulants, or resin-fiber composites.
[0013] The present invention provides in one embodiment a new blend
of an epoxy coating with an ebonite coating with a mix ratio of
95/5 to 5/95. The resulting composition has greatly increased
adhesion to steel and excellent resistance to undercut corrosion
when subjected to salt spray.
[0014] The blends of this invention start from two major
components: Part A: a liquid ebonite composition and Part B: a high
bake epoxy composition.
1 Part A: Liquid ebonite composition Ingredient Mass % A-1 Liquid
rubber 15-85 (a) Compatible liquid unsaturated rubber (>50% of
A-1) (b) Non-compatible liquid unsaturated rubber (c) Liquid
saturated rubber (<10% of A-1) A-2 Sulfur vulcanization agent
10-50 A-3 Vulcanization activator 1-35 A-4 Vulcanization
accelerator 0.2-5 A-5 Carbon black 1-10 A-6 Fillers 0-5 A-7
Additives 0-65 A-8 Crosslinker for A-1 0-35 Total 100
[0015]
2 Part B: High bake epoxy composition Ingredient Mass % B-1 Epoxy
resin 35-75 B-2 Silica 0-25 B-3 Thixotropic Agent 0-5 B-4 Pigments
and fillers 0-40 B-5 Epoxy curing agent 12-65 Total 100
[0016] The mix ratio of Part A/Part B is from 5/95 to 95/5 by mass.
The mixing of Part A and Part B can be carried out just before the
coating application, i.e., they can be supplied as a dual component
system. Alternatively, Part A and Part B can be premixed and
supplied as a single component coating. The composition of the
blends according to the present invention contains at least six key
ingredients: an epoxy resin, an epoxy curing agent, at least an
unsaturated liquid rubber that is compatible with an epoxy, sulfur,
a vulcanization accelerator and a vulcanization activator.
[0017] A-1 is selected from a mixture of liquid unsaturated rubbers
that have different molecular mass or functional groups so long as
they do not react to each other under ambient condition with the
provision that at least 50% by mass of the mixture contains a
liquid rubber that is compatible with the epoxy resin in Part
B.
[0018] The liquid rubber (A-1) has the general formula of:
F.sub.1--(CH.sub.2--CR.sub.1.dbd.CH--CH.sub.2).sub.x--(CH.sub.2--CR.sub.2R-
.sub.3).sub.y-M.sub.2-F.sub.2
[0019] Where
[0020] R.sub.1=H, CH.sub.3, Cl
[0021] R.sub.2, R.sub.3=H, CH.sub.3, C.sub.2H.sub.5, phenyl,
nitrile, acrylate, acetate, vinyl, Cl, Br, etc.
[0022] F.sub.1, F.sub.2=H, CH.sub.3, OH, COOH, NH.sub.2, NCO,
epoxy, vinyl, acrylate, methacrylate, anhydride, etc.
[0023] M is the third monomer, which can be Ethylidene norbornene,
hexadiene or dicyclopentadiene, etc.
[0024] When F.sub.1 and F.sub.2 are either H or CH3, the liquid
rubber is called non-functional. The liquid rubber can be linear
which contains two chain ends, or branched which contains more than
two chain ends or functional groups. The liquid rubber can also be
partially epoxidized or maleinized through its double bonds.
[0025] Preferably, 5<x+y+z<150, and, most preferably,
50<x+y+z<120, so that the molecule is liquid at ambient
temperature. The molecular mass of the liquid rubber can be from
200 to 10,000, preferably from 1000 to 8000, and, most preferably,
from 2500 to 6000.
[0026] Also, at least 50% by mass of the total liquid rubber should
be substantially unsaturated rubbers which have x/(x+y+z)>0.5 so
that there are sufficient double bonds for sulfur vulcanization.
The substantially unsaturated liquid rubbers can be polybutadiene,
polyisoprene, poychloroprene, styrene butadiene copolymer, nitrile
rubber (butadiene acrylonitrile copolymer), etc. Optionally, the
liquid rubber can contain up to 10% by mass of substantially
saturated liquid rubbers which have x/(x+y+z)<0.1 as modifier or
compatibilizer. The substantially saturated liquid rubber can be
butyl, chlorobutyl, bromobutyl, ethylene propylene copolymer,
ethylene propylene diene copolymer, ethylene vinylacetate
copolymer, acrylic rubber, etc.
[0027] Furthermore, at least 50% by mass of the total liquid rubber
should be substantially compatible with the epoxy resin (B-1) in
part B so that the final mixture does not show phase separation.
The epoxy compatible liquid rubber can be epoxidized rubber,
maleinized rubber, arylic functional rubber, chloroprene rubber,
etc.
[0028] Some commercial liquid rubber can be utilized, including
hydroxyl terminated polybutadiene Polybd 45HTLO and Polybd R-20 LM
from Atofina, Liquiflex H and Liquiflex P from Petroflex, Krasol
LBH from Kaucuk, hydroxyl terminated polyisoprene Poly IP from
Atofina, isocyanate terminated polybutadiene Krasol LBD, Krasol NN,
and Krasol NH from Kaucuk, maleinized polybutadiene Krasol LBM from
Kaucuk, Ricon MA from Ricon Chemicals, epoxidized polybutadiene
Polybd 600E, Polybd 605E and Polybd PRO 5052 from Atofina,
nonfunctional polybutadiene Krasol LB, Krasol PS, Krasol PP from
Kaucuk, Ricon from Ricon Chemicals, isolene polyisoprene and DPR
liquid natural rubber from Elementis, Ricon copolymer for butadiene
and styrene from Ricon Chemicals, acrylic terminated polybutadiene
Ricacryl from Ricon Chemicals, etc.
[0029] A-2 can be rubber makers sulfur such as Redball Superfine
supplied by International Sulfur or insoluble sulfur such as
Crystex supplied by Flexsys, or their equivalents. Optionally, a
portion of the sulfur can be replaced by an organic sulfur donor
compound such as Sulfasan DTDM supplied by Harwick Chemicals, or
its equivalents.
[0030] A-3 can be metal oxides or metal organic salts. For example,
zinc oxide is commonly used as activator during sulfur
vulcanization reaction with unsaturated rubber. Magnesium oxide or
other metal oxides are sometimes used. The metal oxides can be
totally or partially replaced with their metallic salts such as
zinc stearate, etc.
[0031] A-4 comprises accelerators for speeding up the sulfur
vulcanization reaction and allowing the reaction to complete either
at a lower temperature or in a shorter time. Commonly used
accelerators include thiurams such as tetramethylthiuram disulfide,
tetrabutylthiruram disulfide, tetraisobutylthiuram disulfide,
tetrabenzylthiuram disulfide, tetraalkylthiuram disulfide,
2-mercaptobenzothiazole, benzothiazyl disulfide,
N-oxydiethylenebenzothiazole-2sulfenamide,
N-cyclohexyl-benzothiazole-2-sulfenamide,
N-tert-butyl-2benzothiazolesulf- enamide, diphenylguanidine,
N,N'-ditolylguanidine, aldehyde-aniline condensation products,
bismuth dimethyldithiocarbamate, cadmium dimethyldithiocarbamate,
cadmium diethyldithiocarbamate, copper dimethyldithiocarbamate,
lead dimethyldithiocarbamate, selenium dimethldithiocarbamate,
selenium diethyldithiocarbamate, tellurium dimethyldithiocarbamate,
zinc dimethyldithiocarbamate, zinc diethyldithiocarbamate, zinc
di-n-butyldithiocarbamate, zinc diamyldithiocarbamate, thiodiazine,
diethylthiourea, trimethylthiourea, dibuylthiourea, zinc isopropyl
xanthate, etc.
[0032] A-5 is carbon black used for color, enforcement or to impart
thermal or electrical conductivity to the ebonite vulcanizates.
[0033] A-6 comprises pigments or fillers that can be added to the
mixture: fly ash, pumice, calcium carbonate, titanium dioxide,
precipitated silica, fused silica, quartz, silicates, barium
sulfide, talc, aluminum oxide, clay, iron oxide, micaceous iron
oxide, glass flake, zinc sulfide, felspar, wallastonite, mica,
grounded rubber particles, zinc borate, etc.
[0034] A-7 comprises additives that can be incorporated into the
mixture, including thixotropic agents, deaerating agents, defoaming
agents, leveling agents, adhesion promoters, surfactants,
dispersing agents, anti-settling agents, fungicides, corrosion
inhibitors, colorants, etc. Optionally, some inorganic moisture
scavenger such as zeolites can also be added.
[0035] A-8 is an optional crosslinker that can react with A-1 and
gel the mixture at ambient condition. This is often necessary to
render the coating tack free for easy handling of coated parts or
for facilitating the second coat. The optional crosslinker contains
at least two functional groups in a molecule that can react with
the functional groups in A-1. For example, if A-1 contains hydroxyl
groups, A-8 can be any diisocyanate or triisocyanate monomers such
as methylene diphenyl diisocyanate (MDI), Isonate 143L supplied by
Dow Chemicals, or it can be an unsaturated liquid rubber which
contains no less than two isocyanate functional groups. The
stoichiometry of A-1 and A-8 is approximately 1 to 1. Those skill
in the arts will have no problem choosing a suitable crosslinker
based on the selection of A-1 and deciding on the amount of A-8 to
adequately crosslink A-1.
[0036] The reaction rate or gel time of A-1 with A-8 must be
carefully adjusted so that the mixture gels and becomes tack free
within a desirable time period such as within 8 hours, but at the
same time there must be a minimum pot life within which a coating
applicator can mix all parts together without significant viscosity
build-up so that the coating can be applied easily onto the
substrate by trowelling, rolling, brushing or spraying. The
required pot life is highly dependent on the application method and
equipment used, typically ranging from about 5 to 240 minutes.
[0037] A-8 can be added at the end of mixing A-1 to A-7 of Part A.
Alternatively, it can be left out from Part A, and be added after
Part A and Part B are mixed. Optionally, a catalyst can be added to
adjust the reaction to achieve the desired pot life and gel
time.
[0038] B-1 epoxy resin can be any bisphenol A diglycidyl ether,
bisphenol F diglycidyl ether, phenolic epoxy, phenol novolac epoxy,
cresol novolac epoxy, tris(hydroxylphenyl)methane triglycidylether,
triglycidyl p-aminophenol, tetraglycidyl amine of
methylenedianiline,
1,3,5-tris(2,3-epoxypropyl)-1,3,5-perhydrotriazine-2,4,6-trione
(triglycidyl isocyanurate), polyglycidylether of
poly(4-hydroxylstyrene), etc. It is preferable that B-1 be in a
liquid form. If it is in solid form, a suitable solvent may be
added to prepare a liquid solution. It is also understood that B-1
can be a mixture of various epoxy resins mentioned above.
[0039] B-2 can be precipitated silica, fumed silica or fused
silica.
[0040] B-3 can be inorganic thixotropic agent such as fumed silica,
bentonites or organic thixotropic agents such as BYK 405 or BYK 410
supplied by BYK Chemie.
[0041] B-4 comprises similar materials as A-6. Part A and Part B
can have the same or different fillers.
[0042] B-5 comprises similar materials as A-5. Part A and Part B
can have the same or different additives.
[0043] B-6 is a curing agent for epoxy resin. The curing agents can
include aliphatic amines, amidoamines, cycloaliphatic amines,
aromatic amines, anhydrides, etc. A description of various curing
agents can be found in the above-referenced "Corrosion Prevention
by Protective Coatings," Chapter 5, Second Edition, by Charles
Munger, published by NACE. It is also understood that B-6 can be a
mixture of various curing agents listed above, so long as they are
physically and chemically compatible.
[0044] Specific embodiments of the present invention are described
in details below by way of examples and comparative examples.
EXAMPLE 1
[0045] Example 1 shows a blending of an ebonite composition and an
epoxy composition at a ratio of 10/90 by mass, according to the
present invention. The effect of the blending is compared with a
control composition consisting of 100% epoxy. The epoxy is cured by
an aromatic amine(Aradur 976-1).
3 Part A: Liquid ebonite composition Ingredient Description Mass %
A-1 Polybd 600E Epoxidized liquid polybutadiene 63.88 (Atofina) A-2
Redball superfine Sulfur (International Sulfur) 22.36 A-3 Kadox 930
Zinc oxide (Zinc Co. of America) 6.85 A-4 Vanax DPG Accelerator (R.
T. Vanderbilt) 1.92 A-5 Vulcan XC-72R Carbon black (Cabot Co.) 4.47
A-7 Tego Glide B1484 Surface modifier (Tego Chemie) 0.26 A-7 Tego
Airex 910 Air release agent 0.26 Total 100.00
[0046]
4 Part B: Liquid epoxy composition Ingredient Description Mass %
B-1 Epalloy 8230 Novolac epoxy (CVC chemical) 59.3 B-2 HiSil 233
Precipitated silica (PPG) 16.6 B-3 Aerosil R972 Fumed silica
(Degussa) 2.0 B-4 Red iron oxide Pigment (Fisher Scientifc) 0.4 B-5
Aradur 976-1 Curing agent (Vantico) 21.7 Total 100.0
[0047] Part A and Part B were mixed with the mass ratio of 10 to
90. A control composition consisting of 100% Part B was also
prepared for comparison.
[0048] First, for each material, a coating with 20 mils thickness
was prepared by using a doctor blade onto a 1/8" steel plate which
was sand blasted to near white metal with 2 mils profile according
to NACE#2 surface preparation standard. Both coated samples were
baked in an air-circulated oven at 175.degree. C. for 4 hours and
120.degree. C. for 24 hrs at the same time. Pull-off adhesion was
conducted according to ASTM D4541 at 23.degree. C. With the blend
the pull-out stress was 3500 psi, compared to the 1700 psi obtained
with the control composition.
[0049] Second, also for each material, a coating with 20 mils
thickness was prepared by using a doctor blade onto a standardized
steel panel (Q-Panel) without sand blasting. Again, both coated
samples were baked in an air-circulated oven at 175.degree. C. for
4 hours and 120.degree. C. for 24 hrs at the same time. The coated
samples were scribed to the steel surface with an X mark and
subjected to outdoor weathering with salt spray test with periodic
spray of salt solution according to ASTM D6675 to test the
resistance to undercut corrosion. After 6 weeks, the control showed
35 mm of corrosion ingress at the interface, while the blend
prepared according to the present embodiment only showed 7 mm of
corrosion ingress.
[0050] This demonstrated that the blending of 10% ebonite into an
epoxy composition significantly increased the adhesion to steel and
the resistance to undercut corrosion of an aromatic amine cured
epoxy.
COMPARATIVE EXAMPLE 1A
[0051] Comparative Example 1A provides evidence that the
significant improvement in adhesion and undercut corrosion
resistance described in Example 1 is not caused solely by mixing
only a compatible liquid rubber into an epoxy composition mentioned
in some prior art. Comparative example 1A was prepared by blending
epoxidized liquid rubber (ingredient A-1) alone with Part B at the
weight corresponding to the epoxy-ebonite blend in Example 1.
[0052] Samples from this material were prepared the same way and
cured at the same conditions as described in Example 1. Pull-off
adhesion and Outdoor weathering with salt spray test was conducted
as described in Example 1. With the PolyBD blended into Part B the
pull-out stress was 1200 psi, compared to the 1700 psi obtained
with the control 100% Part B. Outdoor weathering with salt spray
test of this material showed 70 mm of undercut corrosion, while the
control showed 35 mm of undercut corrosion.
[0053] This demonstrated that adding epoxidized liquid rubber
alone, without the rest of ebonite composition ingredients, is not
the cause of twice as high adhesion measured by pull-out stress
test, neither the cause of significant improvement in undercut
corrosion resistance reported in Example 1.
COMPARATIVE EXAMPLE 1B
[0054] Comparative Example 1B provides evidence that the
significant improvement in adhesion and undercut corrosion
resistance described in Example 1 is not caused solely by the
addition of sulfur, as mentioned in U.S. Pat. No. 4,389,501.
[0055] Comparative example 1B was prepared by adding sulfur
(ingredient A-2) alone into Part B, using a high speed disperser,
at the weight corresponding to the epoxy-ebonite blend in Example
1. Samples from this material were prepared by the same way and
cured at the same conditions as described in Example 1. Pull-off
adhesion and outdoor weathering with salt spray test was conducted
as described in Example 1. With only the sulfur dispersed into Part
B the pull-out stress was also 1200 psi, compared to the 1700 psi
obtained with the control of 100% Part B. Outdoor weathering with
salt spray test showed 55 mm of undercut corrosion, while the
control only showed 35 mm of undercut corrosion.
[0056] Again, this demonstrated that adding sulfur alone, without
rest of ebonite composition ingredients, is insufficient in
improving the adhesion strength or the undercut corrosion
resistance reported in Example 1.
COMPARATIVE EXAMPLE 1C
[0057] The Comparative Example 1C examined the effect of the
compatibility between liquid rubber and epoxy resin. The ebonite
composition (Part A) in the Comparative Example 1C is the same as
that in the Example 1, except that a non-epoxidized liquid rubber,
Polybd 45HTLO, was used in the formulation to replace Polybd 600E,
which is epoxidized.
[0058] Comparative example 1C was prepared by mixing the
non-epoxidized liquid rubber based ebonite composition and Part B
with the mass ratio of 10 to 90. It was observed that the mixture
showed some phase separation.
[0059] Samples were prepared and tested at the identical way as
described in Example 1 and compared with the same control which is
100% Part B. With the blend of non-epoxidized rubber based ebonite
formulation the pull-out stress was 1500 psi, compared to the 3500
psi obtained with the epoxidized rubber based ebonite formulation,
both compared to the 1700 psi obtained with the control.
[0060] On the other hand, outdoor weathering with salt spray test
indicates that complete ebonite formulation even with
non-epoxidized liquid rubber as a base, can still improve the
undercut corrosion protection of the liquid epoxy composition.
Outdoor weathering with salt spray test showed 3 mm of undercut
corrosion compared to the 7 mm obtained with the epoxidized rubber
based ebonite formulation, while control showed 35 mm undercut
corrosion.
[0061] Thus, it showed that using a less compatible liquid rubber
in the ebonite component is still effective in improving undercut
corrosion, but is ineffective in increasing pull-out adhesion
strength.
EXAMPLE 2
[0062] Example 2 shows another blending of an ebonite composition
and an epoxy composition at a ratio of 10/90 by mass, according to
the present invention. The effect of the blending is compared with
a control composition consisting of 100% epoxy. The epoxy is cured
by an aliphatic amine (Ancamine 2432).
5 Part A: Same as Example 1 Part B: Ingredient Description Mass %
B-1 Epalloy 8230 Novolac epoxy (CVC-Specialty 42.3 Chemicals) B-2
Nubiefer EF MIO Micaceous iron oxide (Nubiola) 10.5 B-3 RCF-015
Glass flake (NGF-Canada) 25.3 B-4 Ancamine 2432 Curing agent (Air
Products) 21.9 Total 100.0
[0063] Part A and Part B were mixed with the mass ratio of 10 to
90. A control using 100% Part B was also prepared for
comparison.
[0064] First, for each material, a coating with 20 mils thickness
was prepared by using a doctor blade onto a 1/8" steel plate which
was sand blasted to near white metal with 2 mils profile according
to NACE#2 surface preparation standard. Both coated samples were
baked at the same time in a air-circulated oven at 180.degree. C.
for one hour. Pull-off adhesion was conducted according to ASTM
D4541 at 23.degree. C. With the blend the pull-out stress was 2600
psi, compared to the 1400 psi obtained with the control.
[0065] Second, also for each material, a coating with 20 mils
thickness was prepared by using a doctor blade onto a standardized
steel panel (Q-Panel) without sand blasting. Again, both coated
samples were baked in an air-circulated oven at 180.degree. C. for
one hour at the same time. The coated samples were scribed to the
steel surface with an X mark and subjected to outdoor weathering
with salt spray test with periodic spray of salt solution according
to ASTM D6675 to test the resistance to undercut corrosion. After
six weeks, the control was significantly delaminated at the
interface with corrosion ingress 25 mm, while the blend according
to this invention only showed 3 mm of corrosion ingress.
[0066] The Example 2 thus demonstrated that the addition of 10%
ebonite to also significantly increased the pull-off adhesion and
undercut corrosion of an aliphatic amine cured epoxy.
COMPARATIVE EXAMPLE 2A
[0067] Comparative example 2A a was prepared by blending epoxidized
liquid rubber (ingredient A-1) alone with Part B given in Example 2
at the weight corresponding to the epoxy-ebonite blend in Example
2.
[0068] Samples from this material were prepared by the same way and
cured at the same conditions as described in Example 2. Pull-off
adhesion and Outdoor weathering with salt spray test was conducted
as described in Example 2. With the Polybd blended into Part B the
pull-out stress was 1200 psi, compared to the 1400 psi obtained
with the control with 100% Part B.
[0069] Outdoor weathering with salt spray test showed 85 mm of
corrosion ingress, while the blend according to this invention only
show 3 mm of corrosion ingress.
[0070] Once again it was confirmed that modification by liquid
rubber alone, without the rest of liquid ebonite formulation
ingredients, is not a cause of tremendous and significant
improvement of corrosion protection reported in Example 2.
COMPARATIVE EXAMPLE 2B
[0071] Comparative example 2B was prepared by mixing sulfur
(ingredient A-2) alone into Part B given in Example 2 at the weight
corresponding to the epoxy-ebonite blend in Example 2.
[0072] Samples from this material were prepared by identical way
and cured at the same conditions as described in Example 2.
Pull-off adhesion and outdoor weathering with salt spray test was
conducted as described in Example 2. With the sulfur dispersed into
Part B the pull-out stress was 2500 psi, compared to the 1400 psi
obtained with the control. Even though that there was a significant
increase in pull-off stress value detected the outdoor weathering
with salt spray test showed catastrophic total delamination of
sulfur modified Part B. Outdoor weathering with salt spray test
showed 85 mm of corrosion ingress, compared with 25 mm ingress of
the control and 3 mm ingress reported in Example 2.
[0073] Again, it showed that mixing sulfur alone can improve
pull-off adhesion strength, but not undercut corrosion of an epoxy
cured by aliphatic amine.
COMPARATIVE EXAMPLE 2C
[0074] Comparative Example 2C illustrates the importance of high
temperature bake of the epoxy-ebonite blends. Epoxy-ebonite blend
described in Example 2 was cured at ambient temperature for 7 days
instead of high temperature bake at 180.degree. C. for one
hour.
[0075] With the ambient temperature cured blend, the pull-off
stress was only 900 psi as compared to 2600 psi obtained with high
temperature bake. Outdoor weathering with salt spray test with salt
spray showed 85 mm of corrosion ingress in the case of ambient
temperature cured versus 3 mm of corrosion ingress of high
temperature bake.
[0076] It thus demonstrated that the high temperature bake is
necessary to achieve either increased adhesion strength or
resistance to undercut corrosion.
EXAMPLE 3
[0077] In Example 3, Part A and Part B are the same as those in
Example 1, but the mix ratio is 50/50 by mass. With the blend
prepared in the mix ratio 50/50 by mass the pull-off stress was
1600 psi as compared to 1700 psi obtained with control. Outdoor
weathering with salt spray test showed 9 mm of corrosion ingress,
while the control showed 35 mm of corrosion ingress. It
demonstrated that the addition of 50% ebonite still enhanced the
resistance to undercut corrosion for the aromatic amine cured
epoxy.
EXAMPLE 4
[0078] In Example 4, Part A and Part B, and the procedure for
sample preparation are the same as those in Example 1, but the mix
ratio is 80/20. With the blend prepared in the mix ratio 80/20 by
mass the pull-out stress was 900 psi as compared to 1700 psi
obtained with control.
[0079] Outdoor weathering with salt spray test showed 3 mm of
corrosion ingress, whereas the control (100% Part B) showed 35 mm
of corrosion ingress
EXAMPLE 5
[0080] In Example 5, Part A and Part B, and the procedure for
sample preparation are the same as those in Example 2, but the mix
ratio is 50/50 by mass. With the blend prepared in the mix ratio
50/50 by mass the pull-off stress was 1800 psi as compared to 1400
psi obtained with control. Outdoor weathering with salt spray test
showed 10 mm of corrosion ingress, but the control show 25 mm of
corrosion ingress. It demonstrated that the addition of 50% ebonite
still enhanced the resistance to undercut corrosion for the
aliphatic amine cured epoxy.
[0081] Although the present invention and its advantages have been
described in detail, it should be understood that the present
invention is not limited to or defined by what is shown or
discussed herein. The tables, description, and discussion herein
illustrate technologies related to the invention, show examples of
the invention and provide examples of using the invention. Known
methods, procedures, systems, elements, or components may be
discussed without giving details, so to avoid obscuring the
principles of the invention. One skilled in the art will realize
that implementations of the present invention could be made without
departing from the principles, spirit, or legal scope of the
present invention. Accordingly, the scope of the invention should
be determined by the following claims and their legal
equivalents.
* * * * *